The present invention relates to a reducing gear; and more particularly, the invention relates to a planetary reducing-type gear interposed between a drive shaft and the input shaft for a dredge pump.
Generally speaking, dredge pumps must be run at different rpm numbers for different phases of operation. For example, during suction, one needs to change the rotational speed of the pump, whenever the soil consistency encountered and its density varies. Removal of the pumped sludge requires still other speeds. The mode change from suction to pumping by means of the same pump is carried out through valves, i.e., switching of valve flaps or the like.
The several switching states, as far as the valves are concerned, are usually associated with particular gear ratios to be changed only when the pump is at rest. Prior to shifting gears, one usually has to empty the suction and pressure lines so that the sludge will not dry and cake to the pipes during the mode change.
Other pumps are known, in which the rotational speed is steplessly, i.e., steadily, adjusted via directly controlled hydrostatic drives, or by means of electric control, or through slip friction clutches. Even though these steady speed control systems do not require stopping the pump for any speed and operational changes, all of these controls are disadvantaged by significant losses in power, up to 20%.